lkml.org 
[lkml]   [2013]   [Apr]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3] [RESEND] mm: Make snapshotting pages for stable writes a per-bio operation
On Tue 09-04-13 14:04:32, Andrew Morton wrote:
> On Tue, 9 Apr 2013 11:06:17 -0700 "Darrick J. Wong" <darrick.wong@oracle.com> wrote:
>
> > + * Here we write back pagecache data that may be mmaped. Since
> > + * we cannot afford to clean the page and set PageWriteback
> > + * here due to lock ordering (page lock ranks above transaction
> > + * start), the data can change while IO is in flight. Tell the
> > + * block layer it should bounce the bio pages if stable data
> > + * during write is required.
>
> I think there are already ab/ba deadlocks between lock_page() and
> journal_start(). iirc one path was write(), I forget which was the
> other path. This was 10+ years ago and nobody else noticed and I
> didn't know how to fix it so I didn't tell anyone ;)
Hum, I don't think they are there anymore ;)

> It would be neat to be able to hook things like journal_start() into
> lockdep but I don't think that lockdep has easy provision for wiring
> oddball things into its mechanisms.
Actually if you look at fs/jbd/transaction.c:start_this_handle(), you
will notice that it is wired into lockdep (the lock_map_acquire() call
there). And it works since I've seen quite some reports from it ;)

Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


\
 
 \ /
  Last update: 2013-04-09 23:41    [W:0.040 / U:0.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site